1. Field of the Invention
The invention relates to the field of connectors, and more particularly to connectors of the flexible variety.
2. Description of the Related Art
Segments of rotating shafts, such as auger shafts, may have to bend. Shafts may be made to bend by fitting them with joints. These joints are required to transfer torque between segments of rotating shafts as well as allowing some axial misalignment of one segment relative to another. Auger sections used with tractors may experience high impact loads when starting. Tractors with high (200+ hp) power motors may produce particularly large impact loads. A tractor that applies a high input power to move a large auger inertia may impart a severe strain on an auger coupling.
Some examples of joints that may be used to connect segments of rotating shafts are universal or constant velocity joints. Splined sections may also be installed between segments of rotating shafts to take up axial displacement of one segment relative to another segment. Sometimes universal or constant velocity joints are combined with splined segments, like a propellor shaft on an automobile. Separate splined section to adjust for length takes up space, and it's difficult to wrap a helical blade around a spline.
A four-prong drive dog may be used to reduce impact by reducing the amount of rotation between the two auger sections before contact. A four-prong drive dog, however, may not allow the spiral planes, i.e. edges of the connecting auger blades to align. Elastic or “rope” drives have been tried as well. Rope drives, however, wind up, storing some energy in the form of deformation before releasing it. Such storage and release impart differences in angular velocities between the shaft segments they connect. These angular velocity differences cause variations in the speeds at which materials proceed through the auger. Speed differences produce local pile-ups of material that may contribute further to clogs and clumps, which may interfere with the auguring process.
Furthermore, a rope or elastic member stretched between two segments of a shaft to impart rotational motion will necessarily be loaded in tension and shear. Elastomers, such as rubber, is often quite weak in tension or shear. An elastic connector may thus load the elastic member where it's weakest, in tension.
Augers may transport granular materials, such as grain, dust or silage. Granular or dusty materials may interfere with the operation of a universal or a constant velocity joint. The joint may become gummed up, and the moving parts of the joint may experience significant wear due to the materials being transported. Furthermore, the sliding surfaces of constant-velocity joints may become contaminated with silt and debris, making the joint work harder. Finally, universal joints, although cheap and robust, impart differences in angular velocities between the shaft segments they connect. These angular velocity differences cause variations in the speeds at which materials proceed through the auger. Speed differences produce local pile-ups of material that may contribute further to clogs and clumps, which may interfere with the auguring process.